The umbilical is a composite structure capable of transporting hydraulic fluids, chemicals, electrical and optical signals and electric power. The conduit for chemical transport is usually placed in the center, while those for electrical signals and power and the hydraulic pipes are placed peripherally around the central element or core element. The peripherally situated elements are usually wound into a helix around the central pipe. Each element is free to move longitudinally in relation to the other elements.
From EP 0 627 027 B1 there is known a method for manufacturing and laying a plurality of elongate elements into an umbilical comprising a core element, a plurality of conduits and/or cables situated outside the core element, filler material around and between the conduits/cables and optionally a protective sheath surrounding the cables/conduits and filler material, which core element is advanced along a feed line and the conduits and/or cables are fed onto the outside of the core element and laid in a helix. The known lay-up machine used in this method is very complex and cannot be used on-site at the installation area, which normally is a platform in the sea.
GB 1 387 180 discloses a hollow cable comprising a tubular support of flexible homogenuous material, high tensile stringers disposed on the external surface of and immediately adjacent the support, and electric conductors disposed parallel to the stringers and in a common layer therewith the electrical conductors having approximately the same transverse dimensions as the stringers. The electrical conductors and the stringers are assembled around the support so as to make a very small angle with the longitudinal axis of the tubular support. A retaining layer is disposed over the stringers and electrical conductors. In one embodiment the support is formed with spacer ribs which extend parallel to the longitudinal axis of the support thereby providing longitudinal grooves to take up the electrical conductors and stringers. The retaining layer prevents the electrical conductors and the stringers from going out from the grooves.
GB 2 178 506 discloses an umbilical device having a longitudinal axis, and comprising at least one elongated electrical cable and/or tube element and an elongated load bearing component along said longitudinal axis and having an external surface including at least one groove disposed along said longitudinal axis and parallel thereof, said component including a central core encompassed by a plastic or elastic layer, which is provided with said at least one groove,